Halogen additives, such as those based on fluorine, chlorine, and bromine, have been used to give flame retardant properties to TPU compositions. In recent years, certain end use applications that contain TPU specify that the TPU composition be halogen free. This has required TPU formulators to search for other flame retardants to replace the previously used halogen additives.
U.S. Pat. No. 6,777,466 assigned to Noveon IP Holding Co. discloses the use of melamine cyanurate as the only organic flame retardant additive in a thermoplastic polyurethane composition.
U.S. Pat. No. 5,837,760 assigned to Elastogram GmbH discloses a self-extinguishing flame retardant, thermoplastic polyurethane that contains one or more organic phosphonates and one or more organic phosphonates mixed with a melamine derivative.
U.S. Pat. No. 5,110,850 assigned to B.F. Goodrich Co. discloses halogen free flame retardant thermoplastic polymers where the sole flame retardant is a melamine that is derivative free.
WO 2006/121549 assigned to Noveon, Inc. discloses a thermoplastic polyurethane containing a flame retardant combination including phosphinate compounds, phosphate compounds and a pentaerythritol and dipentaerythritol component.
Still, there exists a need in the art for effective non-halogenated flame retardant combinations that impart flame retardant characteristics to thermoplastic polyurethane compositions while not impairing mechanical strength and processability.